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Analphylatoid reaction is caused by non-IgE mediated histamine released. Intravenous N-acetylcysteine (NAC) infusion is well known to cause analphylatoid reaction. However, it’s incidence is unknown.
Recently, a large retrospective study of all patients who received 21-hour IV NAC in 34 Canadian hospitals (1980 to 2005) was performed.
Anaphylactoid reaction was documented in 528 (8.2%) of 6455 treatment courses
- Cutaneous reaction (urticarial, pruritus and angioedema) occurred in 398 (75.4%)
- Systemic reaction (respiratory symptoms or hypotension): 34 (6.4%)
- Both reactions: 96 (18.2%)
Over 90% patients developed analphylatoid reaction within 5 hours.
Onset of reaction:
- 1stNAC dosing (150 mg/kg over 1 hour): 133/528
- 2ndNAC dosing (50 mg/kg over 4 hours): 371/528
- 3rdNAC dosing (100 mg/kg over 16 hours): 24/528
Administered medication for treatment
- Antihistamine: 371
- Beta-2 agonist: 15
- Epinephrine: 10
- Corticosteroids: 7
Patient characteristics that were associated with higher incidence of Anaphylactoid reaction includes
- Female
- Single acute ingestion
- Low serum acetaminophen level.
Bottom line
- Anaphylactoid reaction to NAC is uncommon
- Cutaneous symptoms are most common
- Female, single acute ingestion and low serum acetaminophen levels are associated with incidence of anaphylactoid reaction.
References
Yarema M et al. Anaphylactoid reactions to intravenous N-acetylcysteine during treatment for acetaminophen poisoning. J Med Toxicol 2018: Jun;14(2):120-127. doi: 10.1007/s13181-018-0653-9. Epub 2018 Feb 8.